Majid became Sultan of Zanzibar and Oman on the death of his father, Sayyid Said bin Sultan, but his accession was contested. Following the struggle over the accession to the position of Sultan of Oman, Zanzibar and Oman were divided into two separate principalities, with Majid ruling Zanzibar and his older brother Sayyid Thuwaini bin Said al-Busaid ruling Oman.

His reign was infamous in that he consolidated his power around the East African slave trade. His descendants would later follow this practice. Barghash bin Said claimed to halt the slave trade, but he continued this until the United Kingdom gained protectorate over the colony.